A Laser Beam Deflection System for Measuring Stress Variations in Thin Film Electrodes

Abstract

The bending beam method for measurements of stress in thin films deposited on an elastic substrate in the form of a thin stripe has been improved by the introduction of a laser beam deflection system and of a laser spot position detector. With this improvement, stress measurements have been performed in situ during the electrochemical reactions of palladium hydride formation and of valve metal anodic oxidation. Stress changes in the thin films of 107 N/m 2 can be measured with a time response better than ls. This allows the detection of rapid reactions (like H diffusion in a Pd thin film) and of the electrostriction effect even in anodic films with thickness below 20 nm.

On the contribution of electrostriction to charge-induced stresses in anodic oxide films

“…Our measured values are also in fair agreement with the measured electrostriction stresses of, respectively, −190 MPa and −200 MPa reported on TiO 2 thin films by Sahu et al [16] and Panagopoulos [17]. In contrast, they are about one order of magnitude larger than the ones predicted by Vermilyea [1], predictions which were based on the simplified Eq.…”

The Electrochemical Degradation of Poly(3,4-ethylenedioxythiophene) Films Electrodeposited from Aqueous Solutions

“…The "electrochemical bending beam" ("bending cantilever") method [61][62][63][64][65][66][67][68][69] …”

Structural changes during the overoxidation of electrochemically deposited poly(3,4-ethylenedioxythiophene) films

“…The "bending beam" method [39][40][41][42][43][44][45][46][47][48][49][50][51] can be effectively used in electrochemical experiments, since the changes of the stress (g f ) in a thin film or other conducting layer on one side of an insulator (e.g. glass) strip in contact with an electrolyte solution can be estimated from the changes of the radius of curvature of the strip.…”